1. Field of the Invention
This invention relates in general to the manufacture of semiconductor devices and in particular to the reduction of metal in a scribe area between semiconductor die areas of a wafer.
2. Description of the Related Art
Copper is used in scribe area interconnect layers of a semiconductor wafer e.g. for test structures and alignment keys. During the singulation of the die areas of a wafer, the copper in the scribe area interconnect layer may build up on a saw blade. This copper build up on the saw blade causes cracking and chipping of the wafer. The cracks and chips may lead to a mechanical failure of the die during its application.
Multiple saw blades may be used for cutting a scribe area to reduce the damage to the substrate of the wafer from the copper buildup on a saw blade. A first saw blade would be used to cut the interconnect layer. Copper build up from the interconnect layer would accumulate on the first saw blade. A second saw blade would follow the same saw path to cut the under laying substrate. Because this second saw blade would not be cutting any copper, little if any copper would build up on this saw blade. However, utilizing two saw blades may cause other problems due to saw misalignment. Also, ledges in the die edge may be created due to the copper build up on the first saw blade in that the saw blade with copper build up may be wider than the second saw blade.
Crack stop trenches located at the die edge may be used to prevent cracking of the die. However, these trenches may require additional processes for patterning, etching of the pattern, removal of the mask, and etching. Furthermore, cracks may propagate beneath the trench into the active area of the die. In addition, with the use of low density dielectric materials having a low dielectric constant in the interconnect layer, trenches in the die may open the die to moisture. Accordingly, it is desirable to reduce the cause of cracking in wafer fabrication.
What is needed is an improved method for reducing the amount of copper or other metals in the saw path to prevent the accumulation of metal on a saw blade or other type of wafer cutting device so as to reduce cracking, chipping, or other damage to the wafer.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted.